A crystalline epoxy resin generally has a rigid or multifunctional main chain skeleton. Therefore, the crystalline epoxy resin shows high heat resistance and is used in fields in which heat resistance reliability is required, such as electrical and electronic fields.
In some fields, molding such as casting molding is impossible for some applications unless a liquid composition is used, and use of the crystalline epoxy resin is restricted to an application using a solid material such as transfer molding. Therefore, the range of use of the crystalline epoxy resin is restricted.
A traditional epoxy resin used in liquid molding such as casting molding is a liquid epoxy resin, and cannot sufficiently meet a demand for improvement in physical properties of a cured product, such as heat resistance, that is currently demanded more and more in fields of adhesion, casting, sealing, molding, laminating, and the like. Therefore, there is an increasing demand for liquefaction of a crystalline multifunctional epoxy resin that imparts physical properties of a cured product, such as high heat resistance.
Examples of a method for producing such an epoxy compound include a method of epoxidizing an olefin by a reaction of olefin-substituted isocyanurate with hydrogen peroxide as an oxidizer using a mixed catalyst containing tungstate or molybdate as a catalyst, a surfactant (a quaternary ammonium salt used as a phase transfer catalyst), and phosphate or phosphonate (see Patent Document 1).
Additional examples thereof include an epoxidation method in which an olefin compound is reacted with hydrogen peroxide in an aqueous pyrophosphate-pyrophosphoric acid solution in the presence of a nitrile compound (see Patent Document 2). Examples of the olefin compound in this method may include: a C3-15 mono-olefin compound such as propylene, 1-butene, t-2-butene, c-2-butene, 1-pentene, isopentene, cyclopentene, 1-hexene, 2-hexene, cyclohexene, norbornene, and 1-octene; a C3-15 polyolefin compound such as butadiene, t-1,3-pentadiene, c-1,3-pentadiene, cyclopentadiene, cyclohexadiene, norbornadiene, cyclooctadiene, and vinylcyclohexene; and a polymer having a carbon-carbon double bond in the molecule such as polyester and polyimide.